The PSP 2000 (Slim & Lite) hasn't been sold new since ~2010. Prices on the secondhand market vary widely based on condition, bundle contents, and region. Below are typical UK/US price ranges for working units:
Add £10–£40 / $15–$50 depending on included games (rare titles like Crisis Core, MGS: Peace Walker add more).
A solid "Good" loose unit around £50/$65 is a fair deal for playing; collectors should target CIB limited editions.